The Triangle

Issue date: 10/5/07 Section: Science and Technology

Media Credit: Ron Tarver, Philadelphia Inquirer Daniel Wolff hoes the weeds down a row of his more than 200 tomato plants growing in a friend's farm in Deptford, N.J. Researchers have found that the smell of soil is caused by geosmin, which is produced by an enzyme found in bacteria and algae.

PROVIDENCE, R.I. - The next time you're digging in your garden, marveling at the sweet smell of Mother Earth, you may want to think of a team of Brown University chemists who recently determined how the warm, slightly metallic smell of fresh soil is produced.

In a paper published this month in Nature Chemical Biology, Professor of Chemistry David Cane, Jiaoyang Jiang GS and Xiaofei He PhD'07 describe the chemical enzyme that produces geosmin, the compound responsible for the sweet scent of soil.

Geosmin, which is Greek for "earth smell," was identified by scientists more than 100 years ago. But it was only recently that chemists began to understand the chemical enzyme that creates this compound, which is responsible for both the aroma of soil and the earthy taste in drinking water. In soil, geosmin is produced by bacteria; in water, blue-green algae make it. More than two years ago, He, working in Cane's lab, discovered that geosmin was being produced when she was working with an enzyme now known as germacradienol-geosmin synthase.

"We didn't find what we started out to find, but actually found things that were even more interesting than expected," Cane said. Cane and Jiang were surprised to discover that a single enzyme present in both the bacteria and the algae was responsible for the creation of geosmin, and in their latest paper, they outlined the precise process by which geosmin is made in nature.

"We didn't start out to say how geosmin was made, but by sharing information with other laboratories and conducting experiments, we were able to find out how it really works. We discovered something that we didn't initially expect at all," Cane said.

Cane and Jiang's discovery has scientists in other fields talking, too. The research team is currently collaborating with a water purification facility in Australia, where microbiologists hope that by understanding the process by which this smelly substance is made, they can work to block its production in water.

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